This invention relates to a multipiece closure for use with sterile containers. More particularly, the invention relates to a retortable composite closure assembly having an outer ring pull for easy opening of sterile containers for pharmaceuticals and the like.
Generally, closures for containers useful in the packaging of pharmaceuticals and the like must be able to maintain an internal sterile condition in order to provide a safe and contamination-free product. The structure and materials of the closure assemblies must be able to withstand sterilization conditions. A retortable closure must also be easy to open and yet be tamperproof to avoid inadvertent opening and to warn of previous opening.
Numerous attempts to satisfy all of the above conditions and provide a convenient and safe closure have not been met with complete success. It is known to provide access to a pierceable closure stopper, of rubber or like material, which is held in place by a metallic cap by having a removable disk portion. U.S. Pat. No. 2,465,269, issued Mar. 22, 1949, provides a central removal disk severed from the cap along arcuate lines but integrally connected to the annular top portion of the cap by frangible ribs. Such a closure is not only difficult to open for the user must pry off the removable disk, but the severance line on the closure provides a source of contamination to the underlying stopper.
It is also known to provide a cover member connected to such an inner removable disk portion which is detachable by fracturable bridge members. The disk includes an opening through which an extension of the cover member protrudes downwardly to engage within the opening to secure the cover member on the disk portion of the outer shell. Opening of the closure is accomplished by pushing upwardly, such as by the user's thumb, against outer portions of the cover which project outwardly beyond the outer edges of the cap as is disclosed in U.S. Pat. No. 3,071,274, issued Jan. 1, 1963.
Variations in the above-described structure for a cover member connected to a removable disk portion are also known. U.S. Pat. No. 3,193,128, issued July 6, 1965, discloses making the extension of the cover member from a reformed hard plastic which is fracturable, thus eliminating the need for a removable disk portion in the metal shell. Another closure assembly includes a score line defining the removable disk portion of the metal shell instead of fracturable connecting bridges and is shown in U.S. Pat. No. 3,587,897, issued June 28, 1971. Reformed plastic is also mentioned in that patent for attaching the cover member to the removable disk.
Still another variation is shown in U.S. Pat. No. 3,358,865, issued Dec. 19, 1967, which includes an upwardly projecting button located on a disk portion of the shell which is removable by breaking frangible bridge members. The button extends through an opening in the cover member and engages over the body portion of the cover to hold the cover in the shell in a locked condition.
It is also known in the art to use ring pull features for opening containers. Though not suitable for sterilized containers, U.S. Pat. No. 3,612,340, issued Oct. 12, 1971, shows a container closure using a metal cap with a tear tab and a sealing liner. The cap has a tear tab secured to an integral rivet part of a raised removable panel which is defined by a score line and is removable when the tab is pulled. It is also known that a stopper may be provided with a gripping ring which is accommodated by an annular space formed around the circular body of a stopper as is shown in U.S. Pat. No. 3,750,820, issued Aug. 7, 1973. A closure cap for providing a sterile seal may also include a cap having a depending skirt and end wall portion having a tear-off cover portion integrally formed in the end wall. The tear-off portion, defined by a weakening groove, is removed by a ring pull integrally formed with the tear-off portion and is shown in U.S. Pat. No. 3,888,377, issued June 10, 1975.
Such prior known closures for providing sterile packaging are not without problems. The lancing in some container closures is a potential source of contamination to the stopper. Furthermore, when using reformed plastic for forming the closure assemblies, there is difficulty in the manufacturing operations in order to control the tearing or breaking of the closure assembly in a desirable manner. Furthermore, the closure assembly may not be a sealed assembly such as when a reformed hard plastic plug is inserted into a hole in a closure cap. Subsequent sterilization of a closure assembly may also adversely affect the closure integrity. Another problem associated with the closures having an overcap is that they are not easy to open. In order to make the closures easy to open with the push of a thumb, the manufacturing tolerances of any fracturable bridges and scoring must be carefully controlled. There exists a need, therefore, for a retortable closure assembly which maintains an internal sterile condition but which is easier to open than prior known closures.